Mobile drafting apparatus with replaceable snap-in units



C. E. JUSTIS May 17, 1966 MOBILE DRAFTING APPARATUS WITH REPLACEABLE SNAP-IN UNITS 2 Sheets-Sheet 1 Filed Aug. 31, 1964 ATTORNEYS May 17, 1966 c. E. JUSTIS 3,251,131

MOBILE DRAFTING APPARATUS WITH REPLACEABLE SNAP-IN UNITS Filed Aug. 31, 1964 2 Sheets-Sheet 2 By m y ATTORNEYS United States Patent 3,251,131 MOBILE DRAFTING APPARATUS WITH REPLACEABLE SNAP-IN UNITS Charles E. Justis, 825 Greenwood Ave., Jenkintown, Pa. Filed Aug. 31, 1964, Ser. No. 393,090

7 Claims. (Cl. 33-80) This invention relates generally to the class of geometrical instruments and is directed particularly to improve ments in drafting apparatus.

The invention is related specifically to drafting apparatus generally known as mobile drafting apparatus wherein a straightedge and a drafting board are coupled together through the medium of a flexible cable or cord which is attached to the board and to the straightedge in such a manner that the straightedge can be moved forwardly and backwardly and maintain a constant parallel relation with any lines drawn along the edge thereof and upon an underlying sheet of drawing paper.

A particular object of the present invention is to provide in an apparatus of the character stated a new straightedge construction embodying a blade having a crown element mounted upon and longitudinally of the top thereof for housing crossed portions of the guiding cable and wherein the crown portion of the blade is detachably connected to the blade in a novel manner which facilitates its easy and quick removal and replacement.

Another object of the invention is to provide in a structure of the above described character an improved cover or housing at each end of the crown for enclosing or covering guide pulleys around which the guide cable passes and wherein such cover or housing is secured in position and joined to the adjacent end of the crown without the use of screws or other fastenings but by means of a novel interengaging connection with the underlying straightedge blade and the adjacent end of the crown.

Another object of the invention is to provide a drafting apparatus of the character described wherein the straightedge blade and pulley covers or housings may be made of a clear plastic and the cable covering crown carried by the blade may also be made either of plastic or metal and wherein the resiliency of the plastic in both the covers and crown, or in the crown alone if made of metal, is utilized to facilitate the establishment of an interlocking coupling between the several units.

More specifically the invention comprises a straightedge construction consisting of the blade, the crown which is in the form of a hollow member, the pulleys and pulley housings, wherein the blade is provded longitudinally of the top side and between and parallel with the straight longitudinal edges thereof, with an undercut or dovetail recess which terminates short of the ends of the blade. The crown has longitudinal flanges which vare adapted, by reason of the flexibility thereof, to be snapped into the longitudinal recess to secure the crown to the blade.

At each end of'the blade there are rotatably mounted thereon a pair of guide cord pulleys which are positioned at opposite sides of the recess and beyond the ends of the recess and the crown.

A cover or housing is provided for each pair of pulleys, which when in position, extends in the transverse direction of the blade and is provided on the side adjacent to the crown, with an opening leading into the crown and with a flange bordering the opening which is of a size to extend into the open end of the crown.

At the opposite side of the housing the wall thereof is provided with a bottom edge lip which, after the flange has been inserted into the open end of the crown, can be forced down into a receiving slot for engagement under a flange bordering the top edge of the slot. Thus the housing is easily snapped into and out of position and when snapped into position it will be firmly held against movement.

The invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawings forming a part of the specification, with the understanding that the invention is not confined to a strict conformity with the showing of the drawings but may be changed or modified so long as such changes or modifications mark no material departure from the salient features of the invention as expressed in the appended claims.

In the drawings:

FIGURE 1 is a view in top plan of a drafting board showing the mobile drafting apparatus of the present invention applied thereon.

, FIGURE 2 is a view in perspective and on an enlarged scale of one end portion of the straightedge structure with a portion of the underlying supporting board.

FIGURE 3 is a sectional view taken substantially on the line 3-3 of FIGURE 2.

FIGURE 4 is a sectional view taken substantially on the line 4-4 of FIGURE 2.

FIGURE 5 is a section taken substantially on the line 5-5 of FIGURE 3.

FIGURE 6 is an exploded view,-on an enlarged scale, and in perspective, illustrating the relationship of units of the straightedge at one end thereof.

FIGURE 7 is a perspective view of a pulley cover lookn: at the outer side thereof.

Referring now more particularly to the drawings, n11- meral 10 generally design-ates a conventional drawing board, the working or top surface of which is designated 12.

The straightedge structure of the present invention is generally designated 14 and is maintained in position for. movement across the working surface of the board by a single lengthof flexible cable or cord 16, operatively connected with the straightedge in the manner hereinafter described.

The straightedge 14 comprises the blade 18 which is of substantial width and of a length to extend substantially entirely across the width of the board 10 as shown in FIGURE 1.

The longitudinal edges 20 of the blade are parallel with one another and form the guide or scribing edges for laying out lines extending transversely of a drawing sheet, not shown, secured upon the surface 12 of the board and upon which the straightedge blade lies, the under side or bottom of the blade preferably being arched or transversely curved as at 22, which stops static.

The end faces 24 of the blade may be fiat as shown and cut square across the width of the blade and the top of the blade is formed with the oppositely inclined surfaces 26 which slope toward the edges 20 and at the high sides of these surfaces they are separated by a narrow fiat top surface 28 which extends a short distance longitudinally of the blade from each end thereof.

The top surface of the blade 18 has formed therein and longitudinally thereof, the relatively wide channel 30.

Patented May 17, 1966 3 This channel is approximately the same width as the flat middle top section 28 of the blade as will be seen particularly upon reference to FIGURE 6.

The channel 30 is of dovetail cross sectional contour whereby the opposite sides thereof have the undercut wall surfaces 32.

Each end of the channel 30 terminates in the upwardly sloping end wall portion 34 which is a continuation of the bottom of the channel, the slope extending upwardly and toward the adjacent end of the blade. Thus each end of the channel 30 terminates short of the end of the blade, being separated from the end by the short flat top surface portion designated 28 in FIGURE 6.

The surface portion 28 has formed therein and transversely thereof, in relatively close proximity to the end of the blade, the slot 36.

The outer side of this slot 36, that is, the side nearest to the end of the blade, is formed with the top edge inwardly projecting lip 38 by means of which. the hereinafter described pulley cover or housing is maintained in position on the blade.

At each end of the blade there are mounted two grooved pulleys around which the cable 16 is trained. Each of these pulleys is designated 40. The pulleys 40 of each pair are disposed at opposite sides of the flat top area or portion 28, each pulley being upon an inclined surface 26.

The pulleys 40 are preferably formed of nylon and each is maintained in position by a rivet 42 which has a head 44 countersunk in the top of the pulley and which passes through the blade and terminates in the recess 46 formed in the underside of the blade.

The numerals 48 and 50 designate washers. The upper washer 48 is interposed between the pulley and the top of the blade and encircles the rivet 42 while the lower rivet 50 lies in the recess 46, surrounding the rivet between the bottom of the recess and the flanged lower end 52 of the rivet.

The pulleys 40 turn freely on the flanged top or head 44 of their supporting rivets as will be readily apparent.

As hereinbefore stated, the cable or cord maintains the straightedge in position for back and forth movement over the surface of the board 10. For the performance of this function, the board has secured in or on the top surface thereof preferably adjacent to each end of the edge 54 which would be the lower edge of the board when in use, the post 56 which is preferably threaded.

Adjacent to the top edge of the board, which edge is designated 58, and also adjacent to each end of this top edge there is secured a pin or post 60. These posts 60 are on a line with the post 56 paralleling the adjacent side edges of the board.

The guide cable or chord 16 has each of its ends secured to a post 56 and the chord extends from one post forwardly or toward the upper edge 58 of the board to the pulley nearest thereto and passes around the pulley and then across the width of the board to the pulley 40 at the opposite side of the board and adjacent to the opposite side of the straight edge from the first mentioned pulley. From this second mentioned pulley the chord passes upwardly to and is wrapped around the pin 60 which is located diagonally across the board from the starting post and it is then carried to the other pin 60 and wrapped around the same and from there to the nearest one of the pulleys 40 from which it passes lengthwise of the straightedge to the opposite pulley on the opposite side of the straightedge and from there to the other one of the posts 56 where the end of the cord is fixed. Thus, it will be seen that the chord or cable passes from the two posts 56 to the two pulleys 4i) nearest thereto and then passes lengthwise of the blade in crossed relation to the other two pulleys 40 and is carried upwardly to and around the uppermost posts 60. With this arrangement, the blade can be slid or moved backwardly and forwardly, or with respect to the edges 58 and 54, upwardly and downwardly across the board and the edges of the blade will maintain their parallel relation with the top and bottom edges of the board at all times.

Between the pairs of pulleys at the ends of the blade the cable is covered and enclosed in a tubular shell or crown which extends longitudinally of the channel 30 and stands up above the top of the blade whereby it not only protects the cable but also provides a means for grasping the straightedge to move it across the board. This tubular crown may be formed of plastic of a suitable flexible character or of flexible metal. The tubular crown is open at its ends and comprises a relatively wide top 60 having the longitudinally extending bordering flanges 62 which are downwardly convergent in the major portion of the widths thereof and then are flared outwardly as at 64. These outwardly flared portions are of a width approximately the same as the vertical widths of the walls 32 of the channel and have approximately the same angle as the walls. Also the outwardly flared portions are initially spaced apart a distance slightly greater than the space between the channel walls 32.

The crown is of a length substantially the same as the length of the channel 30 and the flanges at the two ends are cut off at an angle to rest against the inclined surface 34 channel when the crown is in position.

In placing the crown in position the side flanges 62 are flexed inwardly or toward one another so as to permit the flared lower edges to be entered into the channel and when the flexed flanges are released the lower edge portions 64 will move apart and engage against the wall surfaces 32 so as to tightly maintain the crown in connection with the blade. The longitudinal edges of the channel 30 are rounded, as indicated at 32a to prevent breakage. The undercut or cut back end edges of the flanges, designated 66, will then rest upon the inclined surfaces 34 at the ends of the channel.

Disposed transversely of each end of the crown 58 and connected therewith and resting upon the top surface of the blade, is a cover or housing 68 for the adjacent pair of pulleys 40. FIGURE 6 shows the inner side longitudinal wall of a pulley cover while FIGURE 7 shows the outer side wall thereof.

Each pulley cover comprises the central top portion 70 which joins the inclined outer end top portions 72 and each of these outer top portions or outer end top portions joins the top of a vertical end wall 74 which is formed with a cord window opening 76. The cord window opening has only top and side edges and these are bordered by narrow outwardly projecting flanges 78. These flanges serve as rub surfaces to protect the cord or cable passing through the window opening in the event that the cord, or cable engages the edge of the opening.

The number designates the inner wall of the housing and the numeral 82 designates the outer wall thereof.

The inner wall 80 has the opening 84 formed therein centrally between the ends of the wall. This wall is herdered by the top cross flange 86 and the vertical side flanges 88 and these flanges are dimensioned to enter the end of the crown 58 across which the cover is positioned for use.

It will be readily seen that the cover or housing 68 at each end of the crown 58 is fully open on its underside and when it is in operative position, the bottom edges of the inner and outer walls will rest directly upon the underlying sloping surfaces 26 of the straightedge blade and the bottom edges of the cross walls or end walls 74 and the lower ends of the vertical portions of the flanges 78 will likewise rest on the surface of the blade as clearly shown in FIGURE 2 and the cord windows will be in position to have the cord portions pass outwardly therethrough as shown in FIGURES 2 and 5.

The outer wall 82 of each cover of housing 68 is continuous from end of the housing to the other as shown in FIGURES 2 and 7. The lower edge of this wall 82 has a downwardly projecting tongue portion 90 which is in the proper position and of the proper length to enter the slot 36 in the portion 28 of the blade and the lower edge of this tongue portion 90 terminates in the outwardly projecting flange 92 which, when the housing is placed in position upon the top of the blade, snaps under thelip 38 so as to lock the cover in place.

In the operation of placing a cover 68 in position, the cover is first tipped or tilted slightly so as to permit the flange 86 to enter the open end of the crown 58 and engage the underside of the top wall 60 of the crown whereupon the outer side of the cover is pressed down and the flange 92, which is slightly transversely rounded as shown, will then slip past the lip 38 and after the flange has reached the underside of the lip the flexed wall 82 or tongue portion 90 thereof will spring out and the flange will snap into position against the underside of the lip.

Since the cover or housing 68 is made of a suitable flexible plastic material it will have suflicient resiliency to permit the engagement of the flange 86 under the top of the crown piece and bend or flex slightly when the outer side of the cover is pressed down to force the tongue 90 into the slot 36 and effect the engagement of the flange 92 with the underside of the lip 38.

'Thus the housing will be firmly retained in position and rest with the bottom edges of the walls thereof upon the underlying surfaces of the blade. At the same time the slight upward pressure or force applied to the top wall 60 of the crown piece 58 will impose an upward pull of the v outwardly flared portions 68 of the convergent flanges 62,

against the undercut faces 32 of the channel 30 thereby further assisting in maintaining the crown tightly in place.

From the foregoing it will be seen that there is provided by the present invention a new and novel construc-v tion for a mobile drafting apparatus wherein the replaceable snap-in units will be maintained firmly in operative position at all times without the necessity of employing screws or other types of individual or separate fasteners. When it should become necessary to remove the housings 68 this is easily accomplished by pressing inwardly upon the outer Wall 82 of the housing, in the central portion thereof, so as to disengage the flange 92 from beneath the holding lip 38 and then lift the housing from position. Removal of the crown element is also effected, as will be readily obvious, by pressing inwardly upon the flexible convergent flanges or side Wall portions 62 so as to disengage the outwardly flared lower edge portions 64 from the undercut side walls of the channel 38.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall Within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

I claim:

1. A straightedge construction for mobile drafting apparatus for use with a stationary guide cable, comprising an elongate blade of substantial width, an elongate tubular crown unit on and extending longitudinally of the medial portion of the blade and terminating at each end short of the adjacent end of the blade, cooperating means between longitudinal side portions of the crown and the blade frictionally securing the crown and the blade together, a pair of pulleys at each end of the crown supported upon the blade and spaced apart transversely of the latter, a cover for each pair of pulleys resting upon the blade and having opposite end window openings for passage therethrough of a guide cable extending through the crown and around the pulleys, and connecting means between one side of each cover and the adjacent end of the crown and between the opposite side of the cover and the blade, detachably interlocking the crown, cover and blade together.

2. A straightedge construction for mobile drafting apparatus for use with a stationary guide cable, comprising an elongate blade of substantial width, an elongate tubular crown unit on and extending longitudinally of the medial portion of the blade and terminating at each end short of the adjacent end of the blade, the crown unit having a top 'and flexible bordering longitudinal side flanges, means carried by the blade engaging said flanges and holding the latter flexed under tension toward one another for removably securing the crown to the blade, a pair of pulleys at each end of the crown supported upon the blade and spaced apart transversely of the latter, a cover for each pair of pulleys resting upon the blade and having opposite end window openings for passage therethrough of a guide cable extending through the crown and engaged around .the pulleys, and connecting means between the one side of each cover and the adjacent end of the crown and between the opposite side of the cover and the blade, detachably interlocking the crown, cover and blade together.

3. The invention as defined by claim 2, wherein the said means carried by the blade engaging said flanges comprises a channel formed in the top of the blade and having undercut opposite longitudinal Walls and the flanges having outwardly flared bottom edge portions extending into the channel and engaged against the surfaces of said undercut walls.

4. A straightedge construction for mobile drafting apparatus for'use with a stationary guide cable, comprising an elongate blade of substantial width having opposite longitudinal drawing instrument guiding edges, the blade having a relatively wide longitudinal medial channel in the top thereof and terminating at its ends a substantial distance short of the adjacent ends of the blade, the blade having a flat top surface portion extending from each end of the channel to the adjacent end of the blade, the channel having undercut longitudinal walls, an elongate tubular crown unit adapted to cover portions of a guide cable, the crown unit having a top and downwardly converging side flanges terminating in outwardly flared edge portions, said outwardly flared edge portions extending into the channel and engaging said undercut walls and the crown unit extending the length of the channel, a pair of pulleys at each end of the channel supported upon the top of the blade and spaced apart transversely of the adjacent flat top surface portion, a cover for each pair of pulleys resting upon the blade and extending across the adjacent fiat top surface portion of the blade, the cover having opposite end window openings for passage therethrough of a guide cable extending through the crown and with the adjacent end of the crown unit, the said inner wall of the cover abutting the end of the crown unit, means carried by said inner wall of each cover engaging in the adjacent end of the crown unit against the underside of the top of the latter each of said covers having an outer longitudinal wall extending transversely of said flat top surface portion of the blade, and means forming an interlocking frictional coupling between the said outer xlrjvalll of each cover and the underlying portion of the blade 5. The invention as defined by claim 4,- wherein the last stated means comprises a slot formed in the said flat top surface portion of the blade below the adjacent cover outer wall and a tongue projecting downwardly from the cover outer wall, the tongue having a flanged edge engaging under a lip on a wall portion of the slot.

6. The invention as defined by claim 5, wherein said side flanges of the crown unit are flexible and are biased to press outwardly whereby to maintain tight engagement between the said outwardly flared edge portions thereof and the walls of the channel, and the said outer wall of i 8 each pulley cover is flexible and the wall and tongue are 7. The invention according to claim 4, wherein the said biased when the cover is in operative position, to move opposite end window openings of the covers are bordered outwardly whereby the tongue flange is pressed tightly into by outwardly projecting flanges. engagement with the adjacent lip and the said means carried by the inner wall and pressed tightly against the 5 N0 Teffifellces Citedunderside of the top of the crown unit, comprises a j flange projecting from said inner wall of the cover at the ROBERT HULL P'mmry Exammerp of the opening therein- 1 H. N. HAROIAN, Assistant Examiner. 

4. A STRAIGHTEDGE CONSTRUCTION FOR MOBILE DRAFTING APPARATUS FOR USE WITH A STATIONARY GUIDE CABLE, COMPRISING AN ELOGNATE BLADE OF SUBSTANTIAL WIDTH HAVING OPPOSITE LONGITUDINAL DRAWING INSTRUMENT GUIDING EDGES, THE BLADE HAVING A RELATIVELY WIDE LONGITUDINAL MEDIAL CHANNEL IN THE TOP THEREOF ND TERMINATING AT ITS ENDS A SUBSTANTIAL DISTANCE SHORT OF THE ADJACENT ENDS OF THE BLADE, THE BLADE HAVING A FLAT TOP SURFACE PORTION EXTENDING FROM EACH END OF THE CHANNEL TO THE ADJACENT END OF THE BLADE, THE CHANNEL HAVING UNDERCUT LONGITUDINAL WALLS, AN ELONGATE TUBULAR CROWN UNIT ADAPTED TO COVER PORTIONS OF A GUIDE CABLE, THE CROWN UNIT HAVING A TOP AND DOWNWARDLY CONVERGING SIDE FLANGES TERMINATING IN OUTWARDLY FLARED EDGE PORTIONS, SAID OUTWARDLY FLARED EDGE PORTIONS EXTENDING INTO THE CHANNEL AND ENGAGING SAID UNDERCUT WALLS AND THE CROWN UNIT EXTENDING THE LENTH OF THE CHANNEL, A PAIR OF PULLEYS AT EACH END OF THE CHANNEL SUPPORTED UPON THE TOP OF THE BLADE AND SPACED APRAT TRANSVERSELY OF THE ADJACENT FLAT TOP SURFACE PORTION, A COVER FOR EACH PAIR OF PUULLEYS RESTING UPON THE BLADE AND EXTENDING ACROSS THE ADJACENT FLAT TOP SURFACE PORTION OF THE BLADE, THE COVER HAVING OPPOSITE END WINDOW OPENINGS FOR PASSAGE THERETHROUUGH OF A GUIDE CABLE EXTENDING THROUGH THE CROWN AND ENGAGED AROUND THE PULLEYS, EACH OF SAID COVERS HAVING AN INNER SIDE WALL PROVIDED WITH AN OPENING IN ALIGNMENT WITH THE ADJCENT END OF THE CROWN UNIT, THE SAID INNER WALL OF THE COVER ABUTTING THE END OF THE CROWN UNIT MEANS CARRIED BY SAID INNER WALL OF EACH COVER ENGAGING IN THE ADJACENT END OF THE CROWN UNIT AGAINST THE UNDERSIDE OF THE TOP OF THE LATTER EACH OF SAID COVERS HAVING AN OUTER LONGITUDINAL WALL EXTENDING TRANSVERSELY OF SAID FLAT TOP SURFACE PORTION OF THE BLADE, AND MEANS FORMING AN INTERLOCKING FRICTIONAL COUPLING BETWEEN THE SAID OUTER WALL OF EACH COVER AND THE UNDERLYING PORTION OF THE BLADE BODY. 